Fortunately, it sounds like he and his family are okay. Here's the story from Mediaite:

“We just found out that [Baier] and his family were in a car accident in Montana,” Colbert said. “Bad, like, jaws of life to get him out of there. They’re all in the hospital but they’re going to be OK. And we just want to say: we hope you’re doing better.”

Colbert continued: “Bret’s message to everyone out there, is: They’re going to be okay, thank you for your thoughts and prayers for him and his family, and please, wear your seatbelt. It makes a difference.”

Bret Baier was apparently skiing at the Yellowstone Club over the weekend: